Ferrite particles are used in various applications. Patent Document 1 (Japanese Patent Laid-Open No. 7-330422) discloses a water quality activating ceramic using ferrite powder as auxiliary material. The ceramic is used as a filtering medium in various devices.
Patent Document 1 discloses that the ferrite particles are used as a filtering medium. However, the ferrite particles are not focused on various properties of individual ferrite particles, do not have a small apparent density with various properties maintained in the controllable state, and do not fill a specified volume with a small amount. So, the filtering medium is not sufficient in the filtration ability.
Patent Document 2 (Japanese Patent Laid-Open No. 2007-320847) discloses products containing a plurality of core-shell ceramic fine particles comprising a core fine particle structure containing a plurality of primary fine particles and a plurality of primary pores and a shell surrounding at least a part of the core fine particle structure. The products include a membrane, a sensor, an electrode, and a getter.
The core-shell ceramic fine particles disclosed in Patent Document 2 include a core of yttrium stabilized zirconia and a shell of lanthanum ferrite. Since lanthanum ferrite is used as the shell, the ferrite particles do not have a small apparent density with various properties maintained in the controllable state and do not fill a specified volume with a small amount.